ASoC: rt5668: remove useless assignments

cppcheck warnings:

sound/soc/codecs/rt5668.c:1177:6: style: Redundant initialization for
'idx'. The initialized value is overwritten before it is
read. [redundantInitialization]
 idx = rt5668_div_sel(rt5668, 1500000, div, ARRAY_SIZE(div));
     ^
sound/soc/codecs/rt5668.c:1174:10: note: idx is initialized
 int idx = -EINVAL;
         ^
sound/soc/codecs/rt5668.c:1177:6: note: idx is overwritten
 idx = rt5668_div_sel(rt5668, 1500000, div, ARRAY_SIZE(div));
     ^

sound/soc/codecs/rt5668.c:1202:6: style: Redundant initialization for
'idx'. The initialized value is overwritten before it is
read. [redundantInitialization]
 idx = rt5668_div_sel(rt5668, ref, div, ARRAY_SIZE(div));
     ^
sound/soc/codecs/rt5668.c:1191:25: note: idx is initialized
 int ref, val, reg, idx = -EINVAL;
                        ^
sound/soc/codecs/rt5668.c:1202:6: note: idx is overwritten
 idx = rt5668_div_sel(rt5668, ref, div, ARRAY_SIZE(div));
     ^

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210302212527.55158-19-pierre-louis.bossart@linux.intel.com


Signed-off-by: Mark Brown <broonie@kernel.org>